To survive the stress encountered during transit in vivo, an erythrocyte must be both durable and flexible. These properties are conferred on the erythrocyte by the cytoskeleton, a network of proteins attached to the inside of the red blood cell membrane. When cytoskeletal proteins are defective or deficient, erythrocytes are subject to lysis. Hemolysis is a symptom of a number of inherited diseases in both man and mouse. In the mouse, there are four types of recessively inherited hemolytic anemias: normoblastic anemia, nb, spherocytic anemia, sph, hemolytic anemia, sphha, and jaundice, ja. All of these mutations in the homozygous condition cause deficiencies of the two erythrocyte cytoskeletal proteins called collectively, spectrin. A basic question can be asked, "Are the mutations a result of alteration(s) in the spectrin structural gene?". Neither the spectrin structural genes nor the mutant genes have been mapped. It is more likely that there is a relationship between the mutant genes and the spectrin structural genes, if the two are linked. To investigate the relationship, we will determine the chromosomal location of the spectrin and mutant genes. The mutant gene will be mapped by standard linkage tests. The spectrin structural gene will be mapped by the following procedures: 1. We will isolate spectrin cDNA from our induced MEL cell cDNA library; 2. We will use the spectrin cDNA clone to isolate mouse genomic clones for spectrin; 3. We will establish the structural organization of the spectrin genes by restriction endonuclease mapping; 4. We will look for restriction enzyme polymorphisms in inbred strains; 5. We will map the spectrin structural genes in recombinant inbred strains generated from inbred lines showing restriction polymorphisms.